1. Field of the Invention
The present invention relates to a propylene-based polymer composition excellent in balance of melt strength, elongation characteristics, and fluidity, and a foamed article thereof.
2. Description of the Related Arts
A propylene-based polymer composition obtained by producing a specific crystalline propylene-based polymer in the first stage and another specific crystalline propylene-based polymer in the subsequent stage, has been conventionally known.
For example, JP-A-55-123637 discloses a sheet of a propylene-based polymer composition composed of: a propylene-based polymer component(1) having an intrinsic viscosity of 4.0 dl/g or less, of 60 to 99.5% by weight; and a propylene-based polymer component(2) having an intrinsic viscosity two times or more that of the component(1), of 0.5 to 40% by weight, obtained by two or more-stage polymerization, the intrinsic viscosity of the total components (1) and (2), exceeding 2.0 dl/g.
Also, JP-A-59-172507 discloses a propylene-based polymer composition excellent in processability and mechanical characteristics, obtained by producing a crystalline propylene-based polymer(1) having an intrinsic viscosity of 1.8 to 10 dl/g, of 35 to 65% by weight, in the first stage, and subsequently producing a crystalline propylene-based polymer(2) having an intrinsic viscosity of 0.6 to 1.2 dl/g, of the remaing amount in the second stage.
Further, JP-A-05-239149 discloses, for example, a propylene-based polymer composition excellent in fluidity and elongation, obtained by producing a crystalline propylene-based polymer(1) having an intrinsic viscosity of 4.3 dl/g, of 8% by weight of the total weight, in the first stage, and subsequently producing a crystalline propylene-based polymer(2) having an intrinsic viscosity of 1.18 dl/g, of the remining amount in the second stage.
Moreover, JP-A-06-93034 discloses a propylene-based polymer composition excellent in mechanical characteristics, obtained by producing a crystalline propylene polymer(1) having an intrinsic viscosity of 2.6 dl/g or more, of 10 to 60% by weight of the total weight, in the first stage, and subsequently producing a crystalline propylene-based polymer having an intrinsic viscosity of 1.2 dl/g or less, of the remaining amount, in the second stage, wherein the ratio of the weight average molecular weight to the number average molecular weight(hereinafter, abbreviated as "Mw/Mn") of the propylene-based polymer is more than 20.
EP-A-736552 discloses a polypropylene having a large Mw/Mn and a high flexural modulus.
WO 94/26794 discloses a polypropylene having a broad molecular weight distribution and an excellent melt strength.
However, the above-described references does not disclose any propylene-based polymer composition excellent in all of the melt strength, elongation characteristics, and fluidity.
The fluidity is important in extrusion, foaming, injection molding, or the like of propylene-based polymers. Generally, a resin having a large fluidity tends to be inferior in melt strength and elongation characteristics. Accordingly, a propylene-based polymer having excellent characteristics in all these terms, and being capable of manufacturing with efficiency has been demanded.